Cable suggestions

That is quite a system for an admitted novice. Aurender suggests that SPDIF is the best choice as an output over USB due to their high quality clocking, and given the choice between bnc and aes, aes will always win. On the other hand it looks like MSB is good at handling USB.

i would definitely upgrade to AES, but I would also try USB. You owe it to yourself to find out which sounds best in your system.

My system is not at that level, so I can only recommend cables I have tried that sound better than the rest. I am sure there are better ones, but it might be best to start with lower cost options and then go up the chain once you decide on a path. Acoustic Zen MC2 AES is a decent cable, and WireWorld Platinum USB is another good choice. I have used both of these and compared them to others and they rose above.

Keep us posted on what you find.

Friend 

Congratulations on building an outstanding system!  MSB makes very high quality gear!  It sounds like a possible compatibility issue - which doesn’t surprise me when dealing with the very temperamental technology of Clocks.  That said, unless the Aurender MC10 is bringing a performance level that you can just cannot be without - you may want to consider replacing it.  

There are many Digital Cable choices out there offering both BNC and AES/EBU connections.  This is such a challenging area due to the unpredictable sonic results any given cable can have with different systems.  For this reason, I srongly suggest visiting www.usedcable.com and picking out a number of cables that can be shipped to you for audition with the allowance of returning the ones you did not like.  This gives you the ability to have some fun swapping out those cables and arriving at the right choice.

Budget?

I have been an advocate of Signal Wire, such as PC Triple C (CCC as some now refer to it), and D.U.C.C, both made by Japanese Companies. I am also informed that Mitsubishi have created a new generation D.U.C.C. wire.

Either of these two wire types used as Signal Path wire is strongly suggested to be investigated. 

Cables will be found of varying values that contain this wire type. 

I do not intend to move on from these wire types, but recently commenced looking at other wires used in Cables made in Japan. This led to learning that there is wire in use that has a metallurgy that is creating a Metal Alloy with Copper (Cu) and gold (Au), where the Gold is the infill metal between the Copper crystals in the wire structure.

The world has changed, and there are top-selling cables in Japan not even known about outside of the country. With the Japanese being renowned metallurgists, before committing to any Cable choice, extending a search and inquiry beyond a forum might produce an end sound much improved in attraction over immediately available options being put to use.

Lending cables is a great way to contain costs and learn a lot about an umbilical's impact on an end sound.

The Links will give an alternate impression of my suggested wire types, and are compared in a review to be read. There are more of these wiire type reviews able to found if a search is done in the link info.

https://highfidelity.pl/@main-515&lang=en

https://highfidelity.pl/@main-749&lang=en

Others may disagree, but I don't think the external clock will enhance performance of your very fine system. The MSB clock will control. In fact, MSB is very clear that its philosophy is that clocking should be handled as close as possible to conversion-which means internally.